In a skillet over low heat, saute chopped mushroom stems and onion in olive oil until tender. Stir in all other ingredients except water.

Sprinkle mushroom caps with salt and fill with sauteed mixture, mounding on top. At this point, your mushrooms can be refrigerated up to 24 hours. Before serving, place water in greased shallow baking dish, arrange mushrooms in dish, and bake for about 20 minutes or until hot all the way through. Serve warm.